Refrigerating process



Aug. 27, 1929. .5. Q CARNEY 1,726,341

REFRIGERATING PRocEss Filed NOV.l 26. 1926 Patented Aug. 27, 1929.

UNITED -STATES ,PATENT OFFICE.

SAMUEL C. CARNEY, I TULSA., OKLAHOMA, ASSIGNOR T0 SHELL PETROLEUM COR- PORATION, A CORPORATION 0F VIRGINIA.

REFBIGEBATING PROCESS.

Application tiled November 26, 1926. Serial No. 150,761.

This invention relates to improvements in refrigerating processes, and consists in the novel procedure hereinafter disclosed.

In a co-pending application, Serial No.

150,759, there is disclosed a process whereby a residual vapor comprising light fractions of hydrocarbon are mixed with a residual condensate and subjected to a refrigerating treatment in an evaporator supplied with a refrigerating agent which is a by-product of stabilizing the gasoline products from the original supply of natural or refinery gas.

Under certain operating conditions, it is desirable to produce a temperature in the evaporator below the freezing point of the condensed water vapor entrained with the fluid under treatment. This water vapor, upon condensation and freezing, where the temperature is low enough to cause freezing, results in the formation of a coating of ice in the passages of the evaporator, which prevents the continued iow of gas through the passages.

It is the purpose of the present invention primarily to provide a method of 'preventing the freezing of the entrained water vapor when it is condensed in the evaporator, but it will be understood that the method also has applicability to refrigerating processes generally Where the solution that is added to the product is insoluble therein.

The process, briefly stated, comprises the injection into the fluid before introduction to the evaporator of a brine solution, meaning thereby generally any composition that will lower the freezing point of the water vapor into the stream of the material under treatment before it enters the evaporator, then separating the injected solution after it has passed through the va orator from the product and maintaining, y suitable means, the original strength of th-e injected solution and recirculating'it to provide a continuous supply for injection into the circulating product.

The process will be better understood by reference to the accompanying drawing, in which there is diagrammatically illustrated a suitable form of apparatus for practicing the invention, it being understood, however, that the illustrated apparatus merely exemplies one suitable form for efficiently carrying out the process.

As illustrated2 the system includes a suppl pipe 1, from which the material tobe treate in the refrigerating cycle is introduced mto aeheat 2 of a refrigerating unit that comprises a series of tubes 3 connected at one end with the head 2 and at the opposite end with a head 4, the product circulating within the tubes and leaving the refrigerating unit through a product discharge pipe 5, by which it is conducted to an accumulator tank 6.

Between the pipes 1 and 5, for convenience, there are provided a by-pa'ss pipe-7 manually controlled by a valve 8 and a by-pass 9 automaticall controlled by a valve 10. The provision o the manually and automatically controlled by-passes is to permit the direct passage of the material from the supply to the discharge pipe without shutting down the line when it is necessary to cut out the evaporator for repair purposes or whenever desired in the operation of the system.

The pipe-1 is equipped with a liquid meter 11 for determining the rate of flow therethrough. The pipe also is equipped with a manually operated valve 12. It will, of course, be understood that the by-pass piping and the provision of the liquid meter is merely for operative convenience and may be omitted without interfering with the operation of the process proper.

In the pipe 1, ahead of the oint where it enters the refrigerating unit, t ere is a Venturi nozzle 13, which is merel an exemplification of one means for intro ucing the supply of brine through a brine supply pipe 14 equipped with a valve 15, the suppl of brine normally being obtained from the ottom of the accumulator tank 6, in which the brine is separated b gravity from the lighter hydrocarbon pro uct.

A number of suitable solutions for injection into the fluid stream are available but, from -a practical standpoint, solutions of sodium chloride or calcium chloride are the most available on account of meeting the necessary conditions of economy and, at the same time, being practically insoluble in hydrocarbon fractions under treatment and being susceptible of considerable dilution by the condensed water vapor without raising the Ifreezing point above a satisfactory operating temperature.

The brine is supplied at a predetermined concentration and in an amount 1n excess of the theoretical amount required to prevent freezing' at a redetermmed temperature when diluted with the amount of water -that will condense in the refrigerating'unit.

- 2 in suchv a quantity The brine passes with 'the material under treatment through the refrigerating element that it will coat the inner surfaces of the evaporator tubes and other parts and therebyl prevent the freezing of the condensed'water vapor. The condensed water vapor is taken upb in the brine solution and essentially there y-dilutes vit to some extent. Provision is, therefore, made for maintaining the necessary degree of concentration b withdrawing a portion of the accumulate brine solutiony from the bottom of the tank 6 through a pipe 16 which is controlled by a valve 17 which may be either automatically or manually controlled, so that the quantity withdrawn for concentration and reintroduction may be determined,` in order to maintain the proper degree of concentration in the supply.

The brine solution is carried by the pipe 16 to a brine concentration tank 18,l which is heated by any suitable means, for instance, by a steam coil `19. The brine concentration tank 18 is held at a pressure lower than the pressure in the tank 6, or ordinary atmospheric ressure, so that the brine, after concentratlon, may be conveniently reintroduced into the tank 6 by means of a blow tank 2O having a valve-controlled inlet passage 21 at the top and a valve-controlled outlet passage 22 at the bottom thereof.

The means brine fr om the concentration tank 18 includes a valve-controlled pipe 23 entering a container 24 within the concentration tank, from which a pipe 25 leads through a vent 26 to the* valve-controlled passage 21. When the brine is'to be elevated from the concentration tank, the valve-controlled passage 22 is closed and a valve 27 'in a pi e 28 eading from the pipe 1 and by whic pressure is normally admitted to the blow tank, is closed so as to shut off the ressure tank 20 from the line 28. The`- va ve-controlled passage 21 is then opened, said passage bein vented at its top in such a manner as to reease the pressure when the valve is open. Now, by ressure admitted through the pipe 23, the Brine is forced upwardly through the vent 26, the gas passing off andthe liquid being carried over to the valve passage 21. After the tank 20` is filled with the concentrated brine, by closing the passa e 21 and opening the valvesy 22 and 27, t e pressure will ualize with that of thev brine accumulator` tank 6 and the concentrated brine from the tank 20 HowsI into the brine accumulator tank without interference with the brine circulation through the tubes of the refrigerating unit. It w1ll be understood that the blow tank 20.is at an elevation above the inlet ofthe passage 22 from the bottom ofthe blow tank to t e tank 6.

n win be understood that the means for.

rentroducing the concentrated brine into the brine accumulator tank is merely a convenient, form of apparatus and that, instead of usingv the blow tank with the jet device, the

concentrated brine can be pumped directv from the concentration tank to the accumulator tank, 'it bein understood that provision must be ma el however, to-prev'ent the drop of pressure in the tank 6. 5

It will be understood that the refrigerating cycle is conducted at a high pressure ranging from approximately two-hundred and fty to three hundred pounds gauge, and it is, therefore, necessary to provide means for re'- introducing the concentrated brine without interfering with this normal operating pressure.

The flow of the'refrigerating agent is through a supply pipe 29 into an evaporating tank 30, the refrigerating liquid being controlled by a liquid level control mecha-' nism 31. The refrigerating liquid-evaporates about the tubes 3 and the vapor is withdrawn through a vapor discharge line 32 having a pressure regulator 33 therein controlled bya thermostat 34, under the influence of the temperature of the product entering the accumulator tank 6. This last described a paratus and its general operation is fully disclosed in \the co-pending application Serial No. 150,759, and as it'is not essentially a part of vthe present process, further description for elevating the concentrated".

thereof is unnecessary;

It will be understood product is conducted from the upper elevation of the tank 6 in such a manner as to completely v.separate it from the accumulated rine, this product being carried over in a pipe 35 to an accumulator tank 36, from which it is discharged through a discharge passage 37', controlledJby a liquid level control mechanism 38. A v

It will be understood that the brine circulation process here disclosed provides a means for preventing freezing of the evaporated water vapor and, at the same time, is so operated as not to interfere with the normal reafter cooling, separating' the hydrocarbon product from theesolution, raising the de- -gree of concentration of the'solution to expel the diluting water vapor carried therewith, an'd returmng the solution to the system-for recirculation.

that the hydrocarbon product from the solution, raising the degreel of concentration of thesolution to expel the diluting water vapor carried therewith, and returning the solution to the system for recirculation.

3. The process of cooling a mixture comrising a component having a relatively low reezin point and a component having a relative y high freezing point, which consists 1n injecting with the mixture an element capable of entering into solution with the relatively high freezing point component and thereby lowering the freezing point thereof below its initial freezing point, subjecting the mixture to a cooling action under pressure,

separating the solution of the relatively high freezing point component from the original mixture by gravity, and returning the said so# lution to the system.

4. The processV of cooling a mixture -in cluding a water component, which consists in injecting with the mixture a solution for lowering the freezing point of said water component into a. coolingarea, said solution being insoluble in the other component of said mixture, separating the added solution with the water component from the mixture by gravity separation, and then returning the separated solution to the system after evaporating the same to' a point to expel an amount of water substantially equal to the water vapor added to the solution in the cooling step.

5. The process of refrigerating a mixture including water as onel of the components thereof, which consists in conductin said mixture together with a solution for lowering the -freezing point of the water component to a cooling zone, and thenseparating the added solution from the product by gravity, evaporating the solution to increase the concentration thereof, and then returningy the same to the system for recirculation.

6. The process of refri erating a mixture comprising components with a high and low .freezing point, which consists in mixing with the same a solution for lowering the freezing point of the high freezing point component and in which the other component is insoluble, subjecting the mixture to a refrigerat' action,l then separating the added solution from the product, and returning the same to the system for recirculation.

7. The process of cooling a mixture comprising a component having a relatively low freezing point and a component having a relatively high freezing point, which consists in injecting with the mixture an. element capable of entering into solution with the rela-v tivelyhigh freezing oint component and thereby loweringthe reezing point thereof below its initial freezing point, subjecting the mixture to a cooling action under pressure, and se arating the solution of the relatively high reezing point component from the original mixture by gravity.

8. The process of refrigerating a mixture comprising components with a high and low freezing point, which consists in mixing with the same a solution for loweringthe freezing' point of the high freezing point component and in which the other component is insoluble, subjectin the mixture to a refrigerating action, and t en separating the added solution from the product.

SAMUEL C. CARNEY. 

